Three-dimensional (3D) display devices add a third dimension (depth) to the viewing experience by providing each of the viewer's eyes with different views of the scene that is being watched. Many 3D display devices use stereo input, which means that two different but related views are provided. This is used, for example, in standard 3D cinema (where glasses are used to separate left and right views for the viewer's eyes). Instead of, for example 50 frames (of image data) a second being provided, in a stereo system 100 frames a second are provided, being 50 for the left eye, and 50 for the right eye. Each frame of a pair comprises a slightly different view of the same scene, which the brain combines to create a three-dimensional image. As a result of the adoption of this technology in 3D cinemas, there is a lot of stereo content available. It is also possible that there are home cinema enthusiasts who will want to replicate the cinema experience at home and build or install stereo projection systems.
However, the use of glasses that are associated with stereo 3D systems is cumbersome for many applications, such as 3D signage and also more casual home 3DTV viewing. Glasses-free systems (also called auto-stereoscopic systems) often provide more than two views of the scene to provide freedom of movement of the viewer, and since the number of views varies, the representation that is often used in these applications is the image+depth format, where one image and its depth map provide the information required for rendering as many views as needed.
A problem that exists with systems that provide parallax information is that the structure of the parallax information (which is additional to the image data), will be optimized for a particular target rendering system or device. For example, if a depth map is provided, then this may be designed with a particular target system in mind. For example, it may be assumed in the creation of the map that the end system is designed to provide 6 different views (the user will only ever see two of the six views, depending upon their position). The choice of 6 views may be based upon what is perceived to be the most likely (or average) configuration of the end system. However the parallax information contained within the signal may not be appropriate for the rendering that will occur at the display device